Furniture caster



lDec. 23 1941. w. F. HEROLD 2,267;403

TTTTTTTTTTTTT R .Patented Dec. 23, 1941 FURNITURE cAs'rEa Walter F. Herold, Easton; Conn., assignor to The Bassick Company, Bridgeport, Conn., a corporation of Connecticut Application Septelnwher 25,1940, Serial No. 358,268

(Cl. 16e-45) Claims.

This invention relates to furniture casters such as employed on office furniture, where the wheel engaging the oor isformed of elastic material, for example, a rubberor rubber-like compound.

In providing casters for desks, chairs, and other furniture used in oiilces wherethe` office iioors have been covered with linoleum or other hard material, it has been the practice to supply a caster wheel having Aa relatively soft and yield ing periphery. Such a wheel would be deformed by the weight imposed upon it to such an extent that it would present a relatively large surface in engagement with the floor, obviating the pitting or denting of the surface, which pitting or denting would take place if the engaging surface of the wheel were too small.

It has been known, however, that caster wheels of the type above mentioned, having relatively soft peripheral portions, have been entirely unsuitable for rooms in which the floors are covered by carpets or rugs. One reason for this is that the soft rubber has a very injurious action on the woven floor covering. The rubber is pressed vor forced into the interstices of the weave in such a manner that when any swivelling action of the caster takes place, there is Wear of the carpet or rug, and in many cases serious damage 4or even destruction, due to the strong pull exerted by the wheel on the nap or pile. Moreover, the swivelling action is seriously interfered with so that the chair cannot be moved in the desired manner. that the use of soft rubber caster wheels on carpets and rugs has been strictly avoided by those familiar with the facts above mentioned, and for a long period of time it has been customary to provide the furniture on carpet-covered floors with wheels having hard and relatively slippery surfaces.

One of the objects of the present invention is to provide a caster wheel which will meet both of the above-mentioned conditions, that is, be usable in a satisfactory manner on either a hard, smooth floor or on a carpeted surface.

Another object is to permit oilice furniture to be provided with casters such that the shifting about of the furniture and the Vallocation of it to carpeted or uncarpeted rooms is a matter of indifference.

To these and otherl ends the invention consists in the novel features and combinations of parts to be hereinafter described and claimed.

In the accompanying drawing:

The result has been' an upwardly extending pin or pintle I3.

Fig. 3 is a vertical partly broken section of the wheel in the condition of Fig. 2, on a greatly enlarged scale;

Fig. 4 is a diagrammatic view comparing the iioor contact area of the wheel selected for illustration with that of a wheel of the same size which is of the kind heretofore used on carpeted iioors; and

Fig. '5 is a fragmentary sectional view of a caster wheel of somewhat modified form.

In meeting ,l the conditions above mentioned, that is, providing a caster wheel or roller which can be used successfully either on a hard, smooth floor or on a carpeted door, I provide a wheel, usually formed by a molding process, in which the body is of a rubber or rubber-,like compound. In order to meet the various conditions, the body in different localities varies in hardness and in other characteristics. In order to be suitable for use on a linoleum surface, for example, the wheel l surface should havethe requisite amount of slipperiness or smoothness in order to reduce as much as possible the wear on the yarns of the fabric.

In the drawing, I have shown a caster having a wheel I0 mounted in the customary manner by an axle II in a horn I2 of the usual type, having The wheel III is molded from rubber and has a hub portion I4 surrounding the usual metallic bushing I5. The hub portion I 4? isat the inner part of a molded rubber body having a relatively hard core portion I4 which extend'swoutwardly to a region near but not at the tread of the wheel.

l The outer limit of this core is indicated in the drawing at I6. From this zone outward the rubber is softer. The softer portion of the rubber is indicated at l1, and this cushion portion extends almost to the periphery or licor-engaging surface of the wheel, butat the periphery there is a relatively thin zone of somewhat harder and yet somewhat flexible or yielding material, as indicated at I 8. The portion I8 is represented as consisting of a thin. hard, yet exible skin or veneer, preferably of rubber, having a thickness of a few thousandths of an inch. vulcanized to the wheel body in such a manner as'to provide an integral structure. The outer surface of this veneer strip is smooth and polished. and preferably, in fact, somewhat glazed so as to reduce friction on a carpet on which the wheel rolls; yet notwithstanding these characteristics of the surface or tread portion of the wheel, the floorcontacting portion iiexes or deforma under full load without breakage or rupture. The deformation of the lower part of the wheel under full load is shown in Fig. 3, which is a transverse section of the wheel, and it will be noted that the tread portion i'iattens substantially, with axial displacement of the soft rubber or cushion portion i1 indicated at il, this displacement causing a perceptible peripheral bulge at each face of the wheel. It will also be observed that the slight crown normally existing in the tread portion of the wheel (shown at the vupper part of Fig. 3) is eliminated at this location, the wheel contacting the floor substantially throughout the width of the wheel, and the veneer strip i8 i'n this portion of the wheel being substantially flat and straight in an axial direction, as shown in the drawing.

In Fig. 4 the hoor-contacting area of the wheel under full load is indicated by the hatched portion 2l. This view, of course, is on a somewhat smaller scale than Fig. 3, but it indicates the relatively large area presented to the floor, which area for a considerable part of the periphery of the wheel extends substantially to the wheel sides. Such as area preventsdentlng or pitting of a linoleum surface. At the lower part of Fig. 4 I have shown diagrammatically the wheel-contacting surface of a hard rubber wheel of the same size such as customarily used on carpeted floors. 'Ihe floor-contacting area of such hard wheel under full load is indicated by the hatched portion 2|.

As regards the relative hardness of the different parts of the wheel, it may be said that I prefer, where the inner core portion of the wheel has a hardness of 100 by a Shores Type A having a hardness of the order of say 60, while the thin but yielding floor-contacting portion I8 has a hardness of 90 or 92, but usually not above 95.

It is preferred that the veneer or skin at the tread be of only slightly less hardness than the core, and that it be able to ex to the position of full load without breaking but have little more than that amount of flexibility.

In the modified form shown in Fig. 5, the separate veneer or skin is replaced by a skin formed as a continuation of the soft rubber portion Il. This may be brought about by a suitable hardening of the surface of the soft rubber portion. In the case illustrated the entire peripheral or tread portion IIh of the soft part is treated to harden it, and also portions i1 at the sides of the wheel. This may be done, for example, by a halogen treatment of that part of the wheel surface which is to be hardened.

The importance of having the floor-contacting surface of the wheel absolutely smooth needs to be stressed. This is not easy to achieve in the production of a molded rubber article.

'If the outer surface of the cushion portion at the wheel periphery is to be hardened by haloduce a glaze and thereby gen treatment or acid treatment, the surface should nrst be prepared with special care, because otherwise the finished article will not have the requisite surface smoothness. With this in mind I recommend prelininary treatment of the.

molded wheels in a rolling barrel for an extended length of time while subjected to an abrasive powder in the presence of a mutable liquid, and with heavy superimposed weight. Buch a treatment will enable the requisite surface smoothness to be attained. After being taken out of the rolling barrel the wheels undergo the treatment for surface hardening of their cushion portions. After contacting their surface portions with a gas or other hardening agent for the required length of time, and the completion of hardening and vulcanization in this manner, the tread surface of the wheel will preferably have a substantial glaze as well as smoothness, so that when the wheel is used on a carpet the latter will receive minimum wear.

Where a separate outer strip is used. its outer surface should be of maximum smoothness and it can be treated in a suitable manner to profurther reduce the coeilicient of friction.

By my invention a wheel is provided which can be satisfactorily used on a smooth hard iioor or on a carpeted door, and therefore in many instances it is unnecessary to manufacture as heretofore the different wheels for different respective uses. Where, for example, in the omces of a large business organization there are rooms with hard, smooth floors and others with carpeted oors, it is no longer necessary w assign a given piece of furniture to a room or keep it in a room having a certain kind of iioor covering. Also, in the case of a carpeted iloor there is in addition to the cushioning of the furniture by the carpet a cushion effect in the caster itself.

While I have shown two embodiments of my invention, it will be understood that the invention can take other forms or embodiments, and that various modifications and changes in details can be made without departing fromthe principles involved or the scope of the appended claims.

What I claim is:

1. A furniture caster having a wheel with an elastic cushion portion therein at the outer part and a relatively harder peripheral floor-engaging skin portion supported by the cushion adapted to ex with said cushion under load on an uncarpeted iloor to engage over an extended area thereof, the hardness of said portion adapting it for use on carpeted surfaces.

2. A furniture caster such as set forth in claim 1, in which the floor-engaging portion has a smooth glazed finish.

3. A furniture caster such as set forth in claim 1, in which the floor-engaging portion is a hardened outer portion of the cushion.

4, A furniture caster such as set forth in claim l, in which the floor-engaging portion is formed as a separate layer vulcanized to the cushion.

5. A furniture caster wheel of resilient material comprising an interior part or core of hard material, a soft cushion surrounding the core, and a flexible rim of only slightly less hardness than the core supported by the cushion and yielding with the cushion under load to conform to the floor over a relatively large area.

WALTER F. HEROLD. 

